How do we know which baby Roof Rat to breed? The rats tell us! In this video, we show 3 babies from the same litter (2 of 6 and Popeye.) Look how obviously different their personalities are!
The three were raised by their mom, and hadn’t spent any time with me before I made the video. Two of them (a boy and girl) are outgoing, brave and friendly. When I hold out my hand to them, they come eagerly and run up my arm (one of them even nibbled my ear!)
One of them is shy and nervous. We squeezes himself into a hiding place, and will not come out when coaxed by me. We have been working with this rat to socialize him and bring him out of his shell, and he’s much friendlier now. Rats are smart, so they can learn to overcome their innate personality traits like excessive shyness. But we won’t breed him, because he would pass this behaviour onto his offspring.
Tameness in rats is multifactorial. In this rat’s case, I assume that his stress response is stronger compared to his siblings. Interestingly, this is possibly controlled just by one gene in their case. The two siblings with the “low stress” version of the gene are friendly, while the “high stress” baby is too fearful to come out of hiding.
In the wild, a higher stress response might help him survive, unless he was so fearful that it kept him from finding food or breeding when people are around. If he had 2 copies of the stress gene, perhaps it would be very hard for him to live in or near human homes, but he might be fine in the wild.
Because the original Roof rats that we used for breeding were found near humans, they had a mix of tame and non-tame genes, so they could breed near humans but still avoid being eaten. By Domesticating them, we are selecting the ones whose genes are of the tame type: they wouldn’t survive in the wild, but they make great pets!
This won’t take hundreds of years. It won’t even take hundreds of generations. The amazing thing is, Our rats already have tameness in their genes! Nature already did the hard work for us. We are just bringing it out of them, in the course of a few short generations. And the rats show us by their behaviour which ones we should breed to achieve that. So, if someone tells you domesticating wild animals is impossible, don’t believe them: now you’ve seen it with your own eyes!